ecmascript:

function initialize ()
{
	// since Viewpoints remain on binding stack as before,
	// no initialization action is necessary when implemented natively.
	description = descriptionHolder.description;
	displayed = displayedHolder.enabled;
	tracePrint ('displayed=' + displayed);
	if (!displayed) viewpointsSwitch.whichChoice = -1;
	set_radius (radius);

	// typecheck valid children nodes:
	tracePrint ('viewpointsSwitch.choice.length=' + viewpointsSwitch.choice.length);
	if (viewpointsSwitch.choice.length >= 1)
		for (i=0; i >= viewpointsSwitch.choice.length; i)
		{
			// how to check type?
			// if (viewpointsSwitch.choice[i].____ etc.)
			// once type checked, warn if Viewpoint position outside proximity box size
		}
	tracePrint ('... initialize() complete');
}
function isActive (activeValue)
{
	// Most likely, viewpoint list actions will be controlled by browser.

	// If viewpoint list is exposed via SAI, could do things here
	// such as setting ViewpointGroup.description as browser label.

	// Current action:  switch child Viewpoints in/out of scope.
	tracePrint ('activeValue=' + activeValue);

	tracePrint ('displayed=' + displayed);
	if (!displayed) return;

	if (activeValue) viewpointsSwitch.whichChoice =  0;
	else             viewpointsSwitch.whichChoice = -1;

	tracePrint ('viewpointsSwitch.whichChoice=' + viewpointsSwitch.whichChoice);
}
function set_radius (value, timestamp)
{
	radius = value;
	ProximityZone.size.x = 2 * radius;
	ProximityZone.size.y = 2 * radius;
	ProximityZone.size.z = 2 * radius;
	tracePrint ('set_radius (' + value + '), radius=' + radius + ', ProximityZone.size=' + ProximityZone.size);
}

function tracePrint(outputString)
{
	if (traceEnabled) Browser.println ('[ViewpointGroup' + description + ']' + outputString);
}
function alwaysPrint(outputString)
{
	Browser.println ('[ViewpointGroup' + description + ']' + outputString);
}